First off, it might not feel like it now but I think it's really good that you're so insightful about your attachment to your therapist. In some ways insight feels rubbish because not knowing is often easier, but actually in the long term it is progress towards building healthier relationships.
Would you feel able to raise this with her? If you didn't want to say everything you could just hint at struggling between sessions due to not having any family/friends support and ask her for some strategies for managing it.
Regarding her attitude towards your transgender friend, it sounds as though you're a really supportive friend to them and it's understandable that you'd be angry at your therapist about that. However, I'd maybe try to keep an open mind as you've only heard one side of the interaction and of course it wouldn't be appropriate for her to discuss her version of events with you. Hopefully, there's been some sort of misunderstanding and if not, unless your friend specifically invites you to support them in raising a complaint, then it's not your battle to fight.